What Is a Build-Over Survey? A Yorkshire Homeowner's Guide

A build-over survey is a CCTV drain survey carried out before building over or within 3 metres of a public sewer. Yorkshire Water requires it as part of a Build Over Agreement (BOA) application — the survey evidences the existing condition and precise route of the sewer, so your extension can be designed and approved safely.

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What Is a Build-Over Survey?

A build-over survey is a specific type of CCTV drain survey done before construction starts on an extension or new building that will be built over, or close to, an existing public sewer.

It typically includes:

• A full CCTV inspection of the sewer running through your property
• Drainage mapping with accurate measurements of pipe depth, gradient, and route
• Defect documentation identifying any cracks, displaced joints, or other issues that need addressing before building over
• A formal report in a format Yorkshire Water (and your local Building Control team) will accept

The output is a document pack that supports your Build Over Agreement application and your building regulations submission.

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When Do You Need a Build-Over Survey?

You need a build-over survey if your proposed extension or new structure will be:

• Directly over a public sewer — at any depth
• Within 3 metres horizontally of a public sewer
• Within 3 metres of a manhole or inspection chamber on the public network

A "public sewer" is one that's adopted by Yorkshire Water — typically anything serving more than one property. Drains serving only your property (private drains) don't usually need a BOA, but Building Regulations Part H still applies and your building control surveyor will want to see drain layouts.

If you don't know whether a sewer near your property is public or private, Yorkshire Water can supply a sewer map (a "sewer search") for a small fee, or your surveyor can assess on site.

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What Is a Build Over Agreement (BOA)?

A Build Over Agreement is formal consent from Yorkshire Water to build over or near their sewer infrastructure. Under the Water Industry Act 1991, water companies have a statutory right to access their sewers at any time. If you build over one without a BOA, Yorkshire Water can require you to demolish what you've built — at your cost.

A BOA contains:

• The agreed location of the build relative to the sewer
• Construction conditions (foundation depth, materials, lintels over the sewer)
• Yorkshire Water's right of access in the future

The build-over survey is the technical evidence the BOA application is built on. Without it, your application either won't progress or will progress more slowly.

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What Does the Survey Process Look Like?

A typical build-over survey for a Yorkshire home follows this sequence:

1. Pre-survey planning

We confirm the location of the proposed extension on a drawing or sketch, and identify the sewer the work will affect. Sewer maps from Yorkshire Water (where available) speed this up.

2. On-site survey

The engineer arrives, locates and lifts the relevant inspection chambers, and runs the CCTV camera through the affected sewer length. This usually takes 1–2 hours.

3. Mapping

With distance markers and ground-level references, the engineer logs the precise route and depth of the sewer. This is what allows your architect or builder to design accurately around it.

4. Reporting

The findings are compiled into a written report with HD video footage, defect coding, and a drawn plan. We deliver in a format Yorkshire Water accepts for BOA applications.

5. Applying for the BOA

You (or your builder) submit the report alongside your BOA application to Yorkshire Water. Approval typically takes 4–8 weeks but can be longer for complex cases.

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What Affects the Cost of a Build-Over Survey?

The cost of a build-over survey depends on a handful of factors:

• The length and complexity of the sewer being surveyed
• Whether mapping with a drawn plan is included (recommended for BOA)
• Number of inspection chambers
• Site access difficulty

For a fixed quote on your specific extension, give us a call — we'll talk through your plans and confirm what's involved before you book. For more on cost factors generally, see our drain survey cost in Yorkshire guide.

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What Happens If the Survey Finds Defects?

If the build-over survey identifies defects in the sewer — cracks, displaced joints, root ingress — Yorkshire Water will usually require those to be repaired before the BOA is granted. This is sensible: building over a damaged sewer locks in the defect and makes future repair far more expensive.

Repairs are typically possible without excavation through no-dig pipe lining (CIPP). We can quote and carry out lining as a continuation of the survey if needed.

The BOA application can then proceed once the repairs are complete and re-evidenced with a follow-up CCTV inspection.

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How Far Ahead Should I Book a Build-Over Survey?

Book the survey at design stage, before drawings are finalised. Knowing the sewer's exact route and depth at this stage allows your architect to:

• Position the extension to avoid the sewer where possible
• Specify deeper foundations or load-spreading lintels where required
• Plan drainage connections sensibly

Booking at the building stage — when foundations are about to be dug — is a false economy. Discovering an undocumented sewer running exactly where your foundations are planned means redesigns, delays, and extra cost.

The BOA itself can take 4–8 weeks, so factoring it into your project programme early avoids holding up the build start. See our drain survey for home extension guide for more on extension planning.

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Frequently Asked Questions

Is a build-over survey the same as a normal CCTV drain survey?

It's a specialised version. The survey method is the same — a camera fed through the drain — but the deliverables are tailored to BOA applications: precise mapping, depth measurements, and a Yorkshire Water-compatible report.

Can I do a build-over survey myself?

No. The survey must be carried out by qualified drainage professionals using calibrated equipment. Yorkshire Water won't accept reports from non-professional sources.

How long does a build-over survey take to complete on site?

A typical residential build-over survey takes 1–2 hours on site. Mapping a complex commercial sewer can take longer.

What if Yorkshire Water won't approve my BOA?

This is rare if the sewer condition is good and the design is reasonable. If approval is refused, the usual reasons are sewer defects (which need repair first), inadequate foundation design, or insufficient access provision. We'll help interpret the response and adjust the design where needed.

Is a build-over survey needed for conservatories, garages, or outbuildings?

If the structure is over or within 3 metres of a public sewer, yes — even for relatively small structures. A conservatory still counts as a permanent structure for BOA purposes.

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Book a Build-Over Survey in Yorkshire

We provide build-over surveys with full drainage mapping across Yorkshire — Leeds, Bradford, Sheffield, Wakefield, York, Harrogate, and beyond — and our reports are accepted by Yorkshire Water and Building Control teams.

📞 Call us on 0113 734 2245

📋 Or fill in our online form for a fast, no-obligation quote.

Same-day surveys available. Reports delivered ready for your BOA application.